ref: b465297573ef0ae41d3a2cdbcb5528f3388ba6d9
parent: cb10287db2a445ae90c5f432e158f141823d1cd9
author: ngkaho1234 <ngkaho1234@gmail.com>
date: Thu Dec 17 17:26:13 EST 2015
ext4_journal: add comments to the code part 1.
--- a/lwext4/ext4_journal.c
+++ b/lwext4/ext4_journal.c
@@ -49,22 +49,45 @@
#include <string.h>
#include <stdlib.h>
+/**@brief Revoke entry during journal replay.*/
struct revoke_entry {+ /**@brief Block number not to be replayed.*/
ext4_fsblk_t block;
+
+ /**@brief For any transaction id smaller
+ * than trans_id, records of @block
+ * in those transactions should not
+ * be replayed.*/
uint32_t trans_id;
+
+ /**@brief Revoke tree node.*/
RB_ENTRY(revoke_entry) revoke_node;
};
+/**@brief Valid journal replay information.*/
struct recover_info {+ /**@brief Starting transaction id.*/
uint32_t start_trans_id;
+
+ /**@brief Ending transaction id.*/
uint32_t last_trans_id;
+
+ /**@brief Used as internal argument.*/
uint32_t this_trans_id;
+
+ /**@brief RB-Tree storing revoke entries.*/
RB_HEAD(jbd_revoke, revoke_entry) revoke_root;
};
+/**@brief Journal replay internal arguments.*/
struct replay_arg {+ /**@brief Journal replay information.*/
struct recover_info *info;
+
+ /**@brief Current block we are on.*/
uint32_t *this_block;
+
+ /**@brief Current trans_id we are on.*/
uint32_t this_trans_id;
};
@@ -84,10 +107,15 @@
#define jbd_alloc_revoke_entry() calloc(1, sizeof(struct revoke_entry))
#define jbd_free_revoke_entry(addr) free(addr)
+/**@brief Data block lookup helper.*/
int jbd_inode_bmap(struct jbd_fs *jbd_fs,
ext4_lblk_t iblock,
ext4_fsblk_t *fblock);
+/**@brief Write jbd superblock to disk.
+ * @param jbd_fs jbd filesystem
+ * @param s jbd superblock
+ * @return standard error code*/
int jbd_sb_write(struct jbd_fs *jbd_fs, struct jbd_sb *s)
{int rc;
@@ -103,6 +131,10 @@
EXT4_SUPERBLOCK_SIZE);
}
+/**@brief Read jbd superblock from disk.
+ * @param jbd_fs jbd filesystem
+ * @param s jbd superblock
+ * @return standard error code*/
int jbd_sb_read(struct jbd_fs *jbd_fs, struct jbd_sb *s)
{int rc;
@@ -118,6 +150,9 @@
EXT4_SUPERBLOCK_SIZE);
}
+/**@brief Verify jbd superblock.
+ * @param sb jbd superblock
+ * @return true if jbd superblock is valid */
static bool jbd_verify_sb(struct jbd_sb *sb)
{struct jbd_bhdr *header = &sb->header;
@@ -131,6 +166,9 @@
return true;
}
+/**@brief Write back dirty jbd superblock to disk.
+ * @param jbd_fs jbd filesystem
+ * @return standard error code*/
static int jbd_write_sb(struct jbd_fs *jbd_fs)
{int rc = EOK;
@@ -144,6 +182,10 @@
return rc;
}
+/**@brief Get reference to jbd filesystem.
+ * @param fs Filesystem to load journal of
+ * @param jbd_fs jbd filesystem
+ * @return standard error code*/
int jbd_get_fs(struct ext4_fs *fs,
struct jbd_fs *jbd_fs)
{@@ -151,6 +193,9 @@
uint32_t journal_ino;
memset(jbd_fs, 0, sizeof(struct jbd_fs));
+ /* See if there is journal inode on this filesystem.*/
+ /* FIXME: detection on existance ofbkejournal bdev is
+ * missing.*/
journal_ino = ext4_get32(&fs->sb, journal_inode_number);
rc = ext4_fs_get_inode_ref(fs,
@@ -175,6 +220,9 @@
return rc;
}
+/**@brief Put reference of jbd filesystem.
+ * @param jbd_fs jbd filesystem
+ * @return standard error code*/
int jbd_put_fs(struct jbd_fs *jbd_fs)
{int rc = EOK;
@@ -184,6 +232,11 @@
return rc;
}
+/**@brief Data block lookup helper.
+ * @param jbd_fs jbd filesystem
+ * @param iblock block index
+ * @param fblock logical block address
+ * @return standard error code*/
int jbd_inode_bmap(struct jbd_fs *jbd_fs,
ext4_lblk_t iblock,
ext4_fsblk_t *fblock)
@@ -196,6 +249,11 @@
return rc;
}
+/**@brief jbd block get function (through cache).
+ * @param jbd_fs jbd filesystem
+ * @param block block descriptor
+ * @param fblock jbd logical block address
+ * @return standard error code*/
int jbd_block_get(struct jbd_fs *jbd_fs,
struct ext4_block *block,
ext4_fsblk_t fblock)
@@ -203,6 +261,9 @@
/* TODO: journal device. */
int rc;
ext4_lblk_t iblock = (ext4_lblk_t)fblock;
+
+ /* Lookup the logical block address of
+ * fblock.*/
rc = jbd_inode_bmap(jbd_fs, iblock,
&fblock);
if (rc != EOK)
@@ -210,6 +271,9 @@
struct ext4_blockdev *bdev = jbd_fs->inode_ref.fs->bdev;
rc = ext4_block_get(bdev, block, fblock);
+
+ /* If succeeded, mark buffer as BC_FLUSH to indicate
+ * that data should be written to disk immediately.*/
if (rc == EOK)
ext4_bcache_set_flag(block->buf, BC_FLUSH);
@@ -216,6 +280,11 @@
return rc;
}
+/**@brief jbd block get function (through cache, don't read).
+ * @param jbd_fs jbd filesystem
+ * @param block block descriptor
+ * @param fblock jbd logical block address
+ * @return standard error code*/
int jbd_block_get_noread(struct jbd_fs *jbd_fs,
struct ext4_block *block,
ext4_fsblk_t fblock)
@@ -236,6 +305,10 @@
return rc;
}
+/**@brief jbd block set procedure (through cache).
+ * @param jbd_fs jbd filesystem
+ * @param block block descriptor
+ * @return standard error code*/
int jbd_block_set(struct jbd_fs *jbd_fs,
struct ext4_block *block)
{@@ -243,13 +316,16 @@
block);
}
-/*
- * helper functions to deal with 32 or 64bit block numbers.
- */
+/**@brief helper functions to calculate
+ * block tag size, not including UUID part.
+ * @param jbd_fs jbd filesystem
+ * @return tag size in bytes*/
int jbd_tag_bytes(struct jbd_fs *jbd_fs)
{int size;
+ /* It is very easy to deal with the case which
+ * JBD_FEATURE_INCOMPAT_CSUM_V3 is enabled.*/
if (JBD_HAS_INCOMPAT_FEATURE(&jbd_fs->sb,
JBD_FEATURE_INCOMPAT_CSUM_V3))
return sizeof(struct jbd_block_tag3);
@@ -256,6 +332,8 @@
size = sizeof(struct jbd_block_tag);
+ /* If JBD_FEATURE_INCOMPAT_CSUM_V2 is enabled,
+ * add 2 bytes to size.*/
if (JBD_HAS_INCOMPAT_FEATURE(&jbd_fs->sb,
JBD_FEATURE_INCOMPAT_CSUM_V2))
size += sizeof(uint16_t);
@@ -264,18 +342,35 @@
JBD_FEATURE_INCOMPAT_64BIT))
return size;
+ /* If block number is 4 bytes in size,
+ * minus 4 bytes from size */
return size - sizeof(uint32_t);
}
-/**@brief: tag information. */
+/**@brief Tag information. */
struct tag_info {+ /**@brief Tag size in bytes, including UUID part.*/
int tag_bytes;
+
+ /**@brief block number stored in this tag.*/
ext4_fsblk_t block;
+
+ /**@brief whether UUID part exists or not.*/
bool uuid_exist;
+
+ /**@brief UUID content if UUID part exists.*/
uint8_t uuid[UUID_SIZE];
+
+ /**@brief Is this the last tag? */
bool last_tag;
};
+/**@brief Extract information from a block tag.
+ * @param __tag pointer to the block tag
+ * @param tag_bytes block tag size of this jbd filesystem
+ * @param remaining size in buffer containing the block tag
+ * @param tag_info information of this tag.
+ * @return EOK when succeed, otherwise return EINVAL.*/
static int
jbd_extract_block_tag(struct jbd_fs *jbd_fs,
void *__tag,
@@ -288,6 +383,7 @@
tag_info->uuid_exist = false;
tag_info->last_tag = false;
+ /* See whether it is possible to hold a valid block tag.*/
if (remain_buf_size - tag_bytes < 0)
return EINVAL;
@@ -304,6 +400,7 @@
tag_info->block = 0;
if (!(jbd_get32(tag, flags) & JBD_FLAG_SAME_UUID)) {+ /* See whether it is possible to hold UUID part.*/
if (remain_buf_size - tag_bytes < UUID_SIZE)
return EINVAL;
@@ -328,6 +425,7 @@
tag_info->block = 0;
if (!(jbd_get16(tag, flags) & JBD_FLAG_SAME_UUID)) {+ /* See whether it is possible to hold UUID part.*/
if (remain_buf_size - tag_bytes < UUID_SIZE)
return EINVAL;
@@ -344,6 +442,11 @@
return EOK;
}
+/**@brief Write information to a block tag.
+ * @param __tag pointer to the block tag
+ * @param remaining size in buffer containing the block tag
+ * @param tag_info information of this tag.
+ * @return EOK when succeed, otherwise return EINVAL.*/
static int
jbd_write_block_tag(struct jbd_fs *jbd_fs,
void *__tag,
@@ -355,6 +458,7 @@
tag_info->tag_bytes = tag_bytes;
+ /* See whether it is possible to hold a valid block tag.*/
if (remain_buf_size - tag_bytes < 0)
return EINVAL;
@@ -367,6 +471,7 @@
jbd_set32(tag, blocknr_high, tag_info->block >> 32);
if (tag_info->uuid_exist) {+ /* See whether it is possible to hold UUID part.*/
if (remain_buf_size - tag_bytes < UUID_SIZE)
return EINVAL;
@@ -389,6 +494,7 @@
jbd_set32(tag, blocknr_high, tag_info->block >> 32);
if (tag_info->uuid_exist) {+ /* See whether it is possible to hold UUID part.*/
if (remain_buf_size - tag_bytes < UUID_SIZE)
return EINVAL;
@@ -407,6 +513,13 @@
return EOK;
}
+/**@brief Iterate all block tags in a block.
+ * @param jbd_fs jbd filesystem
+ * @param __tag_start pointer to the block
+ * @param tag_tbl_size size of the block
+ * @param func callback routine to indicate that
+ * a block tag is found
+ * @param arg additional argument to be passed to func */
static void
jbd_iterate_block_table(struct jbd_fs *jbd_fs,
void *__tag_start,
@@ -422,6 +535,7 @@
tag_start = __tag_start;
tag_ptr = tag_start;
+ /* Cut off the size of block tail storing checksum. */
if (JBD_HAS_INCOMPAT_FEATURE(&jbd_fs->sb,
JBD_FEATURE_INCOMPAT_CSUM_V2) ||
JBD_HAS_INCOMPAT_FEATURE(&jbd_fs->sb,
@@ -441,6 +555,7 @@
if (func)
func(jbd_fs, tag_info.block, tag_info.uuid, arg);
+ /* Stop the iteration when we reach the last tag. */
if (tag_info.last_tag)
break;